This invention relates generally to combustion gaskets. More particularly, this invention relates to combustion gaskets for fuel injectors in internal combustion engines.
Many internal combustion engines use fuel injectors to provide fuel to the cylinders. In a typical configuration, fuel injectors are mounted on the cylinder head in specially designed injector ports. Each fuel injector protrudes slightly into a cylinder to provide fuel at the proper time during the engine""s combustion cycle. Most fuel injectors operate using high-pressure hydraulic fluid. The pressure of the hydraulic fluid changes depending upon the operating condition of the engine.
The fuel injectors must be held in place. If not secured, the high-pressure hydraulic fluid and combustion gases will cause the injector to move out of position. The position of injector also may shift because the hydraulic pressure and combustion gases fluctuate throughout the engine""s combustion cycle. In a typical engine configuration, a clamp, bolt, or similar retaining device holds each fuel injector in place.
In addition, the fuel injector must be properly sealed against the cylinder head. If not properly sealed, combustion gases may enter the injector port and damage the fuel injector and other engine parts. In conventional designs, a combustion gasket is disposed between the fuel injector and the cylinder head. For an effective seal, there must be sufficient loading to compress the gasket against the sealing surface. There must not be excessive loading of the gasket. Excessive loading over compresses the gasket, essentially eliminating its sealing capability. In addition, the load on the gasket will cause creep relaxation if the gasket is not properly designed.
The loading from the retaining device on the fuel injector complicates matters. During assembly, installation, and maintenance procedures there is a tendency to make sure the fuel injectors are well secured. The loading from the retaining device may over compress the gasket initially and increase the creep relaxation of the gasket over time.
In addition, the combustion gasket needs to accommodate variations in the connection of the fuel injector and the cylinder head. The fuel injector may shift in the injector port due to the manufacturing tolerances for the injector and/or the cylinder head. This shifting may increase the load on one part of the combustion gasket and decrease the load on another part of the combustion gasket. Also, the sealing surfaces may be blocked by surface finish aspirates and foreign material from removal and cleaning processes.
The combustion gaskets in conventional designs are usually made of one of the following materials: dead soft copper (solid or embossed), aluminum (solid or embossed), embossed stainless steel, rubber coated embossed stainless steel, clad stainless steel (one or both sides with copper, nickel, silver, gold, etc.), graphite or graphite-filled composite wrapped with stainless steel, or folded ferrous and non-ferrous materials. Some engine designs seat the fuel injector on a taper, which creates a metal-to-metal seal.
These conventional combustion gaskets do not effectively seal the connection of the fuel injector to the cylinder head. Some are sufficiently resilient to seal the connection. However, they do not resist creep relaxation nor do they adapt effectively to accommodate any shifting of the injector. Other designs resist creep relaxation, but are not sufficiently resilient to adequately seal the connection.
Accordingly, there is a need for a combustion gasket resistant to creep relaxation and sufficiently resilient to seal the connection between a fuel injector and a cylinder head under various environmental conditions.
The present invention provides a combustion gasket that resists creep relaxation and is sufficiently resilient to seal the connected surfaces. The combustion gasket has a rigid material structure adjacent to a resilient material structure. The rigid material structure is made from stainless steel or another material that can bear the loading from the fuel injector and resist creep relaxation. The resilient material structure is made from dead soft copper, aluminum, an elastomer, or other material that can adapt to seal the connection between a fuel injector and a cylinder head or similar connected surfaces.
The rigid and resilient material structures are press fitted together. In an alternate embodiment, they are interlocked together. The resilient material structure is adjacent to a peripheral edge of the rigid material. The material structures may be connected directly or separated by other materials, layers, and a gap. The resilient material structure is thicker than the rigid material structure.
The rigid and resilient material structures independently engage the connected surfaces. In the case of a fuel injector, the connected surfaces are an injector ledge formed by the fuel injector and a cylinder ledge formed by the cylinder head. The rigid material structure bears the load of the fuel injector. The resilient material structure is compressed sufficiently to seal the connected surfaces, but not over compressed. The rigid material may partially seal the injector, creating an xe2x80x9corificexe2x80x9d to reduce the flow of combustion gases. In this configuration, the rigid and resilient material structures form a double seal of the connected surfaces.
The following drawings and description set forth additional advantages and benefits of the invention. More advantages and benefits are obvious from the description and may be learned by practice of the invention.